<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        /* 今天先了解border，后面还需要深入讲解border */
        div{
            /* border: 10px solid red; */
            width: 300px;
            height: 300px;

            border-top: 10px solid blue;
            border-right: 10px dashed red;
            border-bottom: 10px solid green;
            border-left: 10px dotted gold;
        }
    </style>
</head>
<body>
    <div>我是一个DIV</div>
</body>
</html>